1. Field of the Invention
The invention relates to varistors and more specifically to varistors having high energy absorption.
2. Summary Of The Prior Art
Voltage dependent resistors are well known in the prior art. In a typical application, the devices are continuously energized with the current increasing dramatically with increased voltage stress to limit the amplitude of the voltage surges.
A prior art patent search was made prior to filing this patent application. During the search the following patents were disclosed as being of interest.
U.S. Pat. No. 4,724,416, discloses varistors including various amounts of Bi.sub.2 O.sub.3, Sb.sub.2 O.sub.3 and SiO.sub.2. U.S. Pat. No. 4,551,268, discloses varistors having boron oxide and silicon oxide.
U.S. Pat. No. 3,905,006, discloses a voltage dependent resistor which includes more than 50 mole percent of SiO.sub.2.
U.S. Pat. No. 3,863,193, discloses a varistor including zinc oxide, bismuth oxide, cobalt oxide, boron trioxide, and at least one member selected from a group consisting of magnesium oxide, calcium oxide, barium oxide, and strontium oxide.
U.S. Pat. No. 3,811,103, discloses voltage dependent resistors, particularly useful in lightning arrestors which include zinc oxide, bismuth oxide, antimony oxide and nickel fluoride.
U.S. Pat. No. 3,760,318, discloses a method for forming voltage dependent resistors.
U.S. Pat. No. 3,760,318, discloses a varistor having ions including sodium diffused in the outer surface.
The above discussed patents are believed to be representative of the prior art.